What it is
The protein p53 is one of the body's strongest defences against cancer, but how it does its job is still being worked out. This study adds a mechanism: p53 switches on chaperone-mediated autophagy (CMA), a selective way for cells to deliver specific proteins to the lysosome for breakdown. The authors find that an energy sensor, AMPK, normally holds CMA back by blocking its receptor (LAMP2A) from assembling, and that p53 sitting in the cytoplasm binds AMPK and lifts that block. Once CMA is active, it degrades two metabolic enzymes, IDH1 and IDH2, which lowers the cell's alpha-ketoglutarate and dampens a glutamine-based metabolic route that tumours lean on, suppressing the growth of lung and liver cancers in the authors' models. Tellingly, cancer-associated p53 mutants fail to turn CMA on, and cancer-driving IDH mutants escape being degraded by it.
Why it matters
p53 is the most commonly mutated gene in cancer, so each new route by which it suppresses tumours is a possible drug target. The work ties three threads together, p53, the cell's protein-recycling machinery, and the metabolic rewiring that cancers depend on, into one pathway. It also offers an explanation for why some p53 mutations are so harmful (they cannot activate this cleanup) and why certain IDH mutations drive cancer (they dodge it), which could help identify tumours that depend on this axis.
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Filed underAutophagy in Disease and Therapy, Cancer-related Molecular Pathways, Heat shock proteins research
